Machine tool



Oct. 10, 1950 N sso 2,525,364

MACHINE TOOL Filed March 1, 1945 2 Sheets-Sheet 1 J6 J5 17 J I? 14- O J]-73 H-H lHhUlN HH IHHHIHH J9 muuuuuuu Q 3% a] I 35 32 l 33 q munINVENTOR MAR L MEN ESSON BY E AT IV Oct. 10, 1950 M. MENNESSON 2,525,364

MACHINE TOOL FiIed Maz ch 1, 1945' 2 Sheets-Sheet 2 'l-NVENTOR-MARGELVMENNESSON BY r I r NE) Patented Oct. 10, 1950 MACHINE TOOL MarcelMennesson, Neuilly-sur-Seine, France, as-

signor to Societe dAppareils de Controle et dEquipment de Moteurs (S. A.Cr M.), (new), a. French society Application March 1, 1945, Serial No.580,414

In France August 14, 1943 Section 1, Public Law 690, August 8, 1946Patent expires August 14, 1963 1 Claim. 1

The present invention relates to machine tools, this expression beingtaken in its most general meaning.

Up to thepresent time, in order to machine a piece on a machine tool toa dimension fixed in advance, use is made of several movementspermitting to displace the piece with respect to the tool or the toolwith respect to the piece and, in in a general manner, permitting allkinds of combinations in the respective displacements of the tool or ofthe piece, the values of these displacements being recorded bymeasurement apparatus of a suitable type. But these measurementapparatus, however accurate they may be, only determined, as a matter offact, the displacements of the piece holding carriage or of the toolholding carriage with respect to a fixed point of the machine at thetime when the measurement is being effected.

When the work is to be made with a high precision, say of the order ofone thousandth of a millimeter, it is found that the variations ofdimensions of the piece as it is being machined do not correspondexactly to the displacement of the tool holder with respect to the pieceholder, or again that several pieces machined in the same manner have,after machining, different dimensions, although the respective positionsof the tool holder and the piece-holder have remained unchanged.

These variations of dimensions result from deformations which take placein the mass of the frames, carriages, tool holders, or piece holders,and which, consequently, cannot be recorded by the measurementapparatus, which only indicate the displacements of each unit withrespect to another unit.

These deformations are caused by bendings, twistings, modifications ofbearing relation, etc.,

which may be of very variable origin and which causes, vary inaccordance with the dimensions I of the piece that is being machined,whereby the final dimensions of the piece depend partly upon the initialdimensions of said piece.

The chief object of the present invention is to provide an improvedmachine-tool which is capable of ensuring more accurate dimensions ofmachining than it had been possible up to now.

With this object in view, according to an essential feature of thepresent invention, the machine-tool comprises, on the one hand, meanstion will be hereinafter described, with reference to the accompanyingdrawings, given merely by way of example, and in which:

Fig. 1 is a diagrammatic vertical section of a machine-tool madeaccording to an embodiment of the invention;

Fig. 2 is aview, similar to Fig. 1, corresponding to another embodiment;

Fig. 3 is a similar view, illustrating a third embodiment of theinvention.

In the following description, I will explain how I make a machine-tool,according to the present invention.

The general organization of this machine-tool is established in anysuitable manner, by providing it, for instance, with the usual means fordisplacing the carriages," piece-holders, or toolholders', and the like.I, 1

According to the present invention, the machine is further provided withmeans for imparting to at least 'some'parts of the machine elementswhich maintain the relative position 'of the piece to be machined withrespect to the tool, a' stress, which will be hereinafter called imposedstress, capable of producing an elastic deformation of these elements.

These means advantageously include an elastic device, such as a spring,the tension of which is adjustable,for' instance by means of a screw, insuch manner as to obtain a high sensitiveness of the means for producingsaid imposed stress.

Advantageously, the means in question are arranged in such manner thatthe imposed stress can be givenan important value with respect to thatof the supplementary stress,

which will be hereinafter referred to as machining stress, resultingfrom the action, or reaction, of the ,piece onthei tool. Advantageously,

as a rule, the imposed stress should be chosen so that the machiningstress produces but a supplementary deformation smaller than thetolerance admitted for the amachining of the piece.

Preferably, the imposed stress is made adjustable or controllable by theperson making use of the machine.

Likewise, I provide measurement apparatus,

advantageously of the pneumatic amplification.-

type, capable of recording theJelasticdeformation of the elementssubjected to the imposed stress? Preferably, these measurementapparatusare disposed and checked so that they directly indicate the relativedisplacements of the piece and the tool under the effect of the elastic:deformation of the elements subjected to the imposed stress.

It will be supposed, by way of example, that these features are appliedto the case of a grinding machine.

According to .the embodiment illustrated .by ,Fig. 1, this machineincludes a frame I carrying a carriage 2 on whichis mounted-the grindingwheel, driven inany suitable manner. This car- ,riage :2 can bedisplaced .with respect to frame I through any suitable control device,such as a threaded rod ,4 operated {by means of a hand Inorder tosupport the piece .6 to be machined, :1

I provide a frame :lmovableparallelly to the axis cferevolution of the-.grinding wheel. I

' Having thusgprovided the elements .of an ordinary grindingmachine, Iadd thereto means capable of exerting on carriage :Zastress tending tomove, for instance, grinding wheel 3 :toward, or away from, piece '6.

For this purpose; for instanceLI make usev of the following elements:

I provide a lever -8 pivoted at .its upper end, located at the samelevel as the point that is .being :machinedpto one end :of.-a--connecting rod l extending in the horizontal-direction, the otherend ofsaiderod {being pivoted to carriage 2. As for the lower end of-lever'8, itr -is=.pivoted"at:9 to frame I.

In-order to make it possible to act upon this lever 8, I provide a handwheel .I I ,.fi-xed to a rod .12 screwed in arknuckle l3 fitted in anintermediate point of .-lever-8. A spring 14 is interposed between handwheel .lul and 'frame I Thus, by compressing spring M, :by screwing ofrod I2, it is possible to produce the imposed stress and to adjust it.

In-order to measure the deformations produced by this .stress, Iprovida'for instance on carriage 2, a measurement apparatus 15 includinga movable portion 16, elastically pushed or otherwise urged toward anadjustable :stationary abutment l l'carried by'frame I. This abutment:lTis-fi-xed in the desired position of adjustment .by a screw H or the.like. Preferably the displacement of the movable portion it :of ,themeasurement apparatus takes place-in ea horizontal plane passing throughthe machining pointer points and the axis of the grinding wheel, and, ina :vertical plane as close as possible to the machining point or points.in question.

.Thus, this measurement apparatus makes it possible .to recordthedisplacements of the grinding wheel with respect to the piece to be,machined, and the working of the machine which has just beendescribed'wi'll be as follows:

In the usual machinesthe adjustment of the grinding wheel withrespect'to'the piece is effected by displacing carriage 2 with respectto the frame I of the machine.

The measurement of this displacement can take place in various'ways andas, as arule, these displacements are very small, they are multiplied byhaving the readings made on a graduated scale carried by hand wheel 5.Now, there exists, inside carriage 2 for instance, deformations betweenthe axis .of the grinding wheel and the points of contact of carriage 2on the frame I of the machine. {These deformations produce a .variationof the:relative positions of the grinding wheel and the rpiece, whichvariations cannot be measured through the usual means since thesedeformations do not exert any reaction on the handwheel Thesedeformations may be constituted, for instance, by a bending resultingfrom the pressure exerted by the piece 6 that is being machined, 0n thegrinding wheel 3.

.On the .otherhand, the bending deformations .of carriage 2 will be themore .important as ,the

pressure exerted'b the grinding wheel on piece 6 are more important,and, as .a matter of fact,

it is .wholly impossible to know what will be the exact dimension (ifpiece 8 after aimachining 0perationas longas the value of thedeformation that takes place in carriage ,2 is unknown.

In order to obviate this drawback, according to the present invention,thecarriage 2 is .subjected, before themachining operation, toadeformation suchthat theactionor the reaction-of piece '5 ongrindingwheel .Shasno disturbingin- .fluence on this deformation. For thispurpose,

it sufficesto exerton carriage 2 a stressing .force o fa valuemuchjhig'her than that of the action or the reaction or piece ,6 ongrinding wheel This stress is produced by. spring l4,.the compression ofwhich is adjustable through Ltheintermediate of hand wheel ,Ll .It isthus possible to .make practically negligible lthereffect of them- ,tionor reaction. of piece 5 on. grinding wheel .3.

The displacements imparted to grinding Wheel .3 'byjthe stress that isimposed vmay be as .high as. some thousandths ofm-illimetenand they willbe measured by means otapparatus l5.

It .will be readily understood that .the fact of ,providing a'lever suchas LI, fitted with a rod 12 screwed in ;a knuckle 13, makes it possibleto displace carriage? over relatively considerable distances. andsubsequently .to readjust, through a corresponding screwing .orunscrewing, the tension of spring I'd .in such manner .as ,to re producethe deformations in carriage 2. In correspondence with such anoperation,.it willbe of .course necessary to perform ,a new readjustment 0f themeasurement apparatus, for instance by making use of the hand operableabutment H which makes it possible .to .take .up relatively considerable.length variations :as ..may occur as a consequence of the displacementof carriage .2 on the frame of the machine.

. Advantageously, "the measurement apparatus will be graduatedexperimentally inany suitable manner in metric units for instance and itwill thus .make it possible .directly to measure:

a. Either the displacement of the ,grinding wheel axis with respectto-the axis of ,pieoe G;- or b. Preferably, in .the .case of acylindrical piece for instance, having .a .rotation movement, thevariation of dimension obtained onethe piece, which variation is equal.to twice the displacement of the tool with respect to .the .piece.

It. is also Tpossible to determine .this .graduation not only on .themeasurement ap aratus, .but al SO On the'hand wheel Il, after a suitabledeterminathe axis of grinding wheel 5 by the deformation of carriage 2.

It is perfectly obvious that the measurement apparatus designated byreference numeral l5 might quite well be located at another place thanthat shown on Fig. 1. Furthermore, it would be possible, owing to apreliminary series of measurements, directly to measure thedisplacements of the axis of grinding wheel 3 even if the measurementapparatus were not located in the plane passing through the axis of thegrinding 5.

wheel and the point where the machining operation is being performed.

Now, if it is supposed that it is desired to apply the invention to acenterless grinding machine, it is for instance possible to proceed inthe following manner:

The frame [3 of the machine (see Fig. 2) carries the working grindingwheel I9, while the driving wheel is carried by a carriage 2| movable inthe usual manner. shown by the drawing, the displacements of carriage 2|are operated by means of a hand wheel 22 mounted on a threaded rod 23fixed in the axial direction with respect to frame 18 and screwed in aportion of carriage 2|. The piece 24 to be machined, in thisconstruction, is placed between the grinding wheels l9 and 2B.

The device for producing the imposed stress is made in the followingmanner:

I provide a threaded rod 25, actuated through a hand-wheel 2B, screwedin a socket 21 capable of sliding in frame I8 and adapted to be fixed inthe desired position by any suitable tightening means such as 28, thisrod extending freely through the carriage 2|.

I interpose a spring 29 between said carriage 2| and a shoulder providedon rod 25 between carriage 21 and frame l8, and another spring,designated by reference numeral 3!), between carriage 2! and thehand-wheel 26, which is located, w th respect to said carriage, on theopposite side from said shoulder.

With such an arrangement, it will be readily understood that thescrewing or unscrewing ,of hand-wheel 25 causes one of the two springs29 and 30 to be compressed and therefore frame l8 and carriage 2! to bebent in one direction or the other, thus causing the axes of the twogrinding wh els to be moved toward, or away from, each other. By givingthese bending deformations. before the working of the pieces,sufficiently considerable values, the action or reaction of piece 24 ongrinding wheels [9 and 20 is practically without influence and thereforeall the pieces, whatever be their dimensions before the machiningoperation, which are treated on the machine are given the same finaldimensions.

In order to measure, as in the case of Fig. 1, the relativedisplacements (chiefly produced by bending deformations) between theaxes of grinding wheels I9 and 20, I may provide a measurement apparatus3| including a movable portion 32 constantly applied in an elasticmanner on an abutment 33 screwed in frame I8 and fixed in position by alock nut 33 The displacements of this movable part 32 advantageouslytake place in a plane passing through the axis of both of the grindingwheels 19 and 20 and in a vertical plane passing as near as pos- Forinstance, as

sible to the points of contact between piece 24 and the two grindingwheels l9 and 20.

For this purpose, for instance, the measurement apparatus 3| issupported by two guides 34' and 35 fixed in carriage -2I and adapted toslide freely through frame l8.

It will be readily understood that the adjustable stop 33 makes itpossible to take up the variations of distance of carriage 2| withrespect to frame 18, which'variations may be rather important, accordingto the dimension of the pieces to be machined; At the same time, socket2! is released by control member 28, in such manner as'to enable thewhole system which produces the bending deformations to have relativelyconsiderable displacements.

Fig. 3 shows how a pneumatic measurement device can be adapted formeasuring the deformations above referred to. In this figure of thedrawings, I'have once more shown, by way of example, a grinding machineconstituted by a frame 36, a grinding wheel holder 31, the grindingwheel 38 of which is driven through means which are not shown, saidgrinding wheel actingup-on a piece 39 supported by a tool holder 49. Thecarriage 31 which holds the grinding wheel can be actuated by theoperator by means of. a hand-wheel 4| provided with the necessary speedreducing gears.

At the upper part of the grinding wheel holding carriage 31, there isfixed a threaded screw 42 which extends through the upper part 46 of thepiece-holder 40. On the right hand side of the figure, the end of rod 42is constituted by a threaded part around which is mounted a sprin 44 thetension of'which is adjusted by means of hand wheel 43.

In order to measure the displacements of grinding wheel 38 with respectto piece 39 due to the elastic deformations of carriage 31 and pieceholder 40 under the action of rod 42 and spring 44, I provide ameasurement apparatus made for instance as illustrated by Fig. 3.

This apparatus includes a device for feeding a chamber opening into thetop end of a pipe 53 with gas at a fixed pressure, and means forproducing, at the other end of said pipe 53, a leak into the atmospherethrough a passage of a section proportional to the displacements to bemeasured. The pressure measured in said chamber thus gives the value ofthese displacements.

'In the embodiment illustrated by the drawing, the gas feed deviceincludes a vessel 54 containing a liquid up to a given level and open tothe atmosphere at its top part. A tube connected at the top with asource of gas under pressure projects into said vessel so as to have itsopen bottom end immersed in the liquid. Thus, the excess of gas escapes,by bubbling through the liquid, into the atmosphere, while gas at athoroughly constant pressure is fed from the top part of said tubethrough a calibrated orifice to the chamber above mentioned. Thischamber is in communication with a pressure gauge 55 and opens into pipe53.

On the other hand, a casing 41, fixed by a screw 48 to the grindingwheel holder 31 has its left hand end in free communication with theatmosphere and its right hand end connected to the lower end of pipe 53.Communication between these ends of casing 41 is controlled by a valvethe stem 52 of which projects from casing 41 on the right hand sidethereof so as to be in contact with a finger 49 carried by piece holder40; the position of finger 49 on said piece holder :anzmsec 40 zbeingzadjust'able :by :means of a screw having a, milled.:head 50 :and heldin position by a lockmut 51.

'Thus, when carriage 3'! and piece holder 40 arecelastically deformed-asthe result of a rotation of hand wheele '4'3, finger'49 pushes 'stem"52, which causes-an opening of the valve .car- Lriedvby i-s'aid stemand a, drop :of the pressure -meas'uredby gauge 55, and, in a generalmanner, :a'll'relativetdisplacements of the respective axes vroffgrind'mg wheel 38 and piece 39 are measured .bYidlSDlECGIIlBIItSIOf theliquid level in pressure gauge 55. I

It is therefore possible, by'rcomparison with other measuring :means',to graduate pressure gauge 5.5 directly in variations of :the distance:between the grinding wheel axis and the piece axis.

This machine works'in the same manner as those of Figs. :1 "and '2. Asuitable rotation of hand :whe'el'1l3 compresses spring 44 andpermits-cfzobtaining a sufiicient deformation of carzria'ge 3'? andipi'ece'iholder 40 for ensuring the feed :of the grinding wheel.

10f course the invention is applicable to all machines in which elasticdeformations influence the dimensions of "the finished piece, and thisindependently idf the nature of the tool that is used (grinding wheel,cutting tool, etc.).

In ,3, general "manner, while I have, in the above description,disclosed what I deem to be practical and efficient em'bodim'ents 'ofthe present invention'it should be well understood'that'I idonot vwishto be limited thereto as there might be "changes 'made in :the"arrangement, disposition and form of the parts without departing fromthe principle of the present invention .as comprehended within the scopeof the-appended claim.

What I claim is:

A machine tool for ,machininga piece which comprises, in combination, aframe, a tool, a piece holder carried by said frame, a tool holderslidable in said frame toward and away from said piece holder, means.for sliding said tool holder in said frame to produce a feed ofthe'tool, a lever pivoted at one end to said-framea link interposedbetween the other end of said lever and said tool holder, a knucklemounted at an intermediate point of said lever, a threaded rod extendingfreely through said frame and said tool holder and adjustably screwed atone end in said knuckle, means at the other end of said rod for screwingit, an abutment near said :last

mentioned rod end, a spring interposed between said abutment and saidframe, and means for adjusting the action of said spring.

MARCEL ME'NNESSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

